Peridot was originally called topazion after the island of Topazios (now Zabargad), an important source of the gem in ancient times. Eventually, the gem came to be named topaz. During the eighteenth century, for reasons that are not clear, the name topaz was re-assigned to the stone we call topaz today, and the name peridot was adopted for the stone represented here. Peridot is most prized when it is dark green without yellow or brown undertones. In early times, peridot was associated with the sun and was believed to possess medicinal powers. Peridot was used during the Crusades to adorn religious objects. It became popular in jewelry during the late 1800's. The gem-quality peridot nodules in this specimen of basalt from Arizona are fragments of the Earth's upper mantle carried to the surface by volcanic eruption.